The primary objective is to find the most suitable radiopharmaceutical for melanoma localization. This will be accomplished by 1) determining, in vitro, tumor specificity and tumor to background ratios, 2) designing the appropriate detection system, using a phantom and an animal model, and 3) clinical trial. Using the Greene melanoma in the hamster we have found that the quinoline derivative, 4-(3-dimethylaminopropylamino)-7-iodoquinoline (hereafter referred to as 43-DMQ), when combined with I-123 enabled localization of both ocular and skin melanoma. Tumor to background ratios are such that imaging has been possible. I-125 labeled quinoline derivatives have been used to localize skin melanoma 1-4 and ocular melanoma 5,6 however, the clear advantages of iodine-123 super 7 are the extremely low dose of radiation to the patient and a photon emission which allows imaging. The increased tissue penetration is particularly important for detection of posteriorly located ocular melanoma, since often a probe cannot be placed closer than 10 to 15 mm (unless there is surgical manipulation). Therefore, the combination of I123 with 4,3 DMQ appears to be ideal. Clinical uses would be detection of 1) ocular melanoma, 2) skin melanoma and 3) metastatic sites. As a model for skin melanoma we have taken the Greene melanoma super 8 in the hamster. With a cell suspension made form this skin tumor we have devised a new technique for producing a model of ocular melanoma in the hamster. The nuclides titanium-45, thallium-201 and lead-203 in ionic and complexed forms are also to be evaluated as localizing agents. Heavy metal localization in melanoma has been reported with thallium-201super 9, however initial results with lead-203 also seem encouraging and the latter offers to be a better isotope super 10. Comparison with radioactive phosphorus 11,12,13 and ultrasound 14, the presently employed modalities for melanoma localization, will be an integral part of the clinical portion of this study.